18. I (to call) my son in Chicago now. I (to want) to call him every month but it(to be) very expensive.

I am calling my son in Chicago now. I want to call him every month but it is very expensive.

Объяснение: 'I am calling' - Present Continuous, потому что звоню сейчас. 'I want' - Present Simple, желание. 'It is' - Present Simple, факт.